Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 010235
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
835 PM MDT MON AUG 31 2015

.DISCUSSION...WEAK ZONAL FLOW OVER THE REGION WILL TRANSITION TO
A SOUTHWESTERLY FLOW BEFORE SUNRISE AS THE TROUGH OFF THE PACIFIC
COAST DEEPENS AND PUSHES FURTHER SOUTH. SKIES WILL BE MOSTLY
CLEAR TONIGHT UNDER THE INFLUENCE OF THIS DRY PATTERN. EXPECTING
WINDS TO PICK UP TUESDAY AFTERNOON AS UPPER LEVEL WINDS MIX DOWN
TO THE SURFACE. FORECAST IS ON TRACK...NO UPDATES.

&&

.AVIATION...VFR ACROSS SE OREGON AND SW IDAHO. ANY SMOKE
LAYERS OR REDUCTION IN VISIBILITY DUE TO WILDFIRE SMOKE WILL BE IN
THE VICINITY OF THE KBKE AND KMYL TERMINALS AND POINTS NORTH AND
WEST. LIGHT SURFACE WINDS OVERNIGHT WILL INCREASE TUESDAY AFTERNOON
ACROSS SE OREGON. W-SW WINDS 15-25 KTS ALOFT THROUGH TUESDAY
AFTERNOON.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH WEDNESDAY...ZONAL FLOW WILL
TRANSITION TO A SOUTHWESTERLY FLOW ALOFT AS AN UPPER TROUGH DIGS
INTO THE PACIFIC NORTHWEST. THE SOUTHWEST FLOW WILL DIRECT A WARM
AND DRY AIR MASS INTO THE AREA ON TUESDAY. HIGHS WILL BE ABOVE
NORMAL. SOME OF THE SOUTHWEST WINDS WILL MIX DOWN TO THE SURFACE
IN THE AFTERNOON FOR GUSTY WINDS ACROSS SE OREGON AND THE HIGHER
TERRAIN OF SW IDAHO. A DRY COLD FRONT WILL MOVE THROUGH TUESDAY
NIGHT. TEMPERATURES WILL BE SEVERAL DEGREES LOWER ON WEDNESDAY
FOLLOWING THE FRONT. ANOTHER COLD FRONT WILL APPROACH THE AREA
FROM THE NORTHWEST...REACHING BAKER COUNTY BY LATE AFTERNOON.
MOISTURE AND INSTABILITY ALONG THE FRONT ARE BOTH MARGINAL...BUT
ENOUGH TO CONTINUE A SLIGHT CHANCE OF SHOWERS. BREEZY SOUTHWEST
WINDS WILL DEVELOP AGAIN DURING THE AFTERNOON...SHIFTING TO THE
NORTHWEST IN BAKER COUNTY BEHIND THE FRONT LATE IN THE AFTERNOON.

LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...MODELS IN FAIRLY
GOOD AGREEMENT BUT DIFFER ON TIMING...PLACEMENT AND AMOUNT OF
PRECIPITATION.  AXIS OF A LONG WAVE TROUGH ALONG THE WEST COAST
WILL BEGIN TO SLOWLY SHIFT EAST WEDNESDAY NIGHT WITH THE BASE OF
THE TROUGH CONTINUING TO DIG SOUTH.  THIS TROUGH SLOWLY OPENS UP
AS IT MOVES EAST WITH THE AXIS OF THE TROUGH OVER THE FORECAST
AREA BY SATURDAY MORNING.  MODELS INDICATED A COLD FRONT WILL
MOVE OVER THE AREA LATE WEDNESDAY NIGHT INTO THURSDAY BUT MODELS
DIFFER ON HOW FAR SOUTH PRECIPITATION WILL BE.  AT THIS TIME
LOOKS LIKE PRECIPITATION WILL BE LIMITED TO BAKER COUNTY OREGON
AND THE WEST CENTRAL MOUNTAINS IN IDAHO.  FRONT SEEMS TO STALL
OVER THE AREA THURSDAY NIGHT AND FRIDAY WITH PRECIPITATION
CONTINUING OVER THE WEST CENTRAL MOUNTAINS.  AS THE AXIS OF THE
TROUGH MOVES OVER THE REGION FRIDAY NIGHT AND SATURDAY
PRECIPITATION WILL BE PUSHED TO THE EAST BUT AS THE AXIS OF THE
TROUGH SHIFTS TO EASTERN IDAHO SATURDAY NIGHT INTO SUNDAY COULD
SEE INCREASING PRECIPITATION FROM THE WEST.  CONFIDENCE IN
LOCATION OF PRECIPITATION OVER THE FORECAST AREA IS LOW BUT
THINKING IS THAT ANY PRECIPITATION WILL BE CONFINED TO NORTHERN
ZONES SUNDAY THROUGH MONDAY.  TEMPERATURES WILL COOL OVER THE
FORECAST AREA AS THE TROUGH MOVES INTO THE REGION.  HIGH
TEMPERATURES ON THURSDAY WILL COOL 10-15 DEGREES FROM WEDNESDAY/S
HIGHS.  TEMPERATURES WILL BE THE COOLEST FRIDAY AND SATURDAY WITH
HIGHS AROUND 70 IN THE LOWEST VALLEYS AND HIGHS IN THE MOUNTAINS
IN THE 60S.  TEMPERATURES WILL SLOWLY WARM SUNDAY AND MONDAY WITH
HIGH TEMPERATURES A FEW DEGREES BELOW NORMAL BY MONDAY.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...AB
AVIATION.....DG
PREV SHORT TERM...BW
PREV LONG TERM....JA/WH



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